There has been recognition that immune system cells and particularly cytotoxic T lymphocytes (CTLs) can be used to detect tumor associated antigens (TAAs). For example, CTLs derived from melanomas have been used to identify a variety of melanoma-specific antigens. See e.g., Bruggen et al., Science, (1991), 254:1643; Bakker et al., J. Exp. Med., (1994), 179: 1005; and Yanuck et al., Cancer Research, (1993), 53, 3257.
Several anti-tumor therapies have attempted to use CTLs to treat diseases such as cancer. In one approach, anti-tumor CTLs are taken from a patient, expanded in vitro, and then given back to the patient to treat the cancer. However, this approach suffers from significant drawbacks. For example, it is not always straightforward to isolate sufficient quantities of the CTLs from the patient. In addition, at least some of the CTLs may have specificities that have survived self-tolerance that could lead to additional complications. See, e.g., Browning et al., Curr. Opin. Immunol., (1992) 4, 613; Mizoguchi et al., Science, (1992), 258:1795, and George et al., J. Immunol., (1994), 152, 1802.
There have been attempts to mitigate these and other shortcomings by making and using recombinant immune molecules such as those resembling antibodies. An antibody has a recognized structure that includes an immunoglobulin heavy and light chain. The heavy and light chains include an N-terminal variable region (V) and a C-terminal constant region (C). The heavy chain variable region is often referred to as “VH” and the light chain variable region is referred to as “VL”. The VH and VL chains form a binding pocket that has been referred to as F(v). See generally Davis Ann. Rev. of Immunology (1985), 3: 537; and Fundamental Immunology 3rd Ed., W. Paul Ed. Raven Press LTD. New York (1993).
Recombinant antibody molecules have been disclosed. For example, several recombinant bispecific antibody (bsFv) molecules have been reported. Most of the bsFv molecules include a F(v) formatted as a single-chain (sc-Fv). More particular sc-Fv molecules include a VH linked to a VL through a peptide linker sequence. See e.g., Huston et al. PNAS (USA), (1988), 85:5879; Bird et al., Science, (1988), 242: 423; WO 94/29350; and U.S. Pat. No. 5,455,030.
Additional bsFv molecules have been disclosed. For example, some bsFv molecules have been reported to bind a T-cell protein termed “CD3” and a TAA. There is recognition that binding of the bsFv may facilitate an immune system response. See e.g., Jost, C. R. (1996) Mol. Immunol. 33: 211; Lindhofer, H. et al. (1996) Blood, 88: 4651; Chapoval, A. I. et al. (1995) J. of Hematotherapy, 4: 571.
There have been attempts to develop straightforward methods of making bispecific antibody molecules. However, many of these attempts have been associated with problems. For example, many of the molecules are reported to be insoluble especially in bacterial expression systems. See e.g., Wels et al., (1992), Biotechnology, 10:1128.
Attempts to make other recombinant immune molecules have been reported. For example, there have been specific attempts to manipulate T-cell receptors (TCRs). The TCR is a membrane bound heterodimer consisting of an α and β chain that resembles an immunoglobulin variable (V) and constant (C) region. The TCR a chain includes a covalently linked V-α and C-α chain. The TCR β chain includes a V-β chain covalently linked to a C-β chain. See generally Davis, supra.
There have been specific efforts to manipulate the TCR by recombinant DNA techniques. For example, in one approach, the TCR has been formatted as a single-chain fusion protein comprising the TCR V regions (sc-TCR). The sc-TCR molecule has been reported to have several important uses. See e.g., Soo Hoo, W. F. et al. PNAS (USA) 89, 4759 (1992); Wülfing, C. and Plückthun, A., J. Mol. Biol. 242, 655 (1994); Kurucz, I. et al. PNAS (USA) 90 3830 (1993); PCT WO 96/13593; PCT WO 96/18105; and Schlueter, C. J. et al. J. Mol. Biol. 256, 859 (1996).
The prior recombinant immune molecules are believed to be associated with significant shortcomings.
For example, there has been recognition that many tumor antigens are “shed” from cells, thereby providing sites for non-specific immune molecule binding. In particular, it has been proposed that many bsFv molecules inadvertently interact with the shed antigens, thereby reducing tumor cell killing efficiency.
The prior immune molecules suffer from additional drawbacks. For example, there has been recognition that many bsFv molecules cannot bind potential target antigens such as certain peptides on the surface of tumor cells. As an illustration, the tumor related protein p53 is usually not expressed on tumor cells as an intact protein. Instead, p53 has been reported to be processed and presented as a peptide in the context of a cell surface class I or class II molecule. Thus, in settings in which binding to specific cell surface peptides is needed, it has been difficult or impossible for bsFv molecules.
Further, it has been difficult to isolate some bsFv molecules without significant isolation and/or re-folding steps. See e.g., Jost, C. R. et al. supra and references cited therein.
Preparation and use of many sc-TCRs has also been associated with problems. For example, several prior methods for making the sc-TCRs have yielded insoluble and improperly folded molecules. Several strategies have been developed in an attempt to improve sc-TCR yields. However, the sc-TCRs produced by these methods often require time-consuming manipulations to obtain even modest amounts of protein. See e.g., Ward, E. S. et al. supra; Schlueter, C. J. supra; and published PCT applications WO 96/18105 and WO 96/13593.
There is a need therefore for recombinant immune molecules and particularly single-chain polyspecific binding molecules that can damage or eliminate (kill) target cells in vitro and in vivo. It would be desirable to have methods for making the polyspecific binding molecules with a minimum of difficult preparative steps.